In the most simple of terms, to have diversification across coin holdings to reduce concentration and risk on a single asset. In addition to the "not all eggs in one basic", accumulating very new coins that have potential, like prior to exchange listings or the change from PoW to PoS, presents an opportunity that's hard to do in any efficient way. You'll be able to add, say, a select group of coins to the manager and it will spend some time mining across the group irrespective of difficulty/hashrate on the network. At a given point of QueenBee maturity, the application will present you with some prospective coins you might not otherwise know of and hopefully identify opportunity.